Method for producing synfuel from biodegradable carbonaceous material

ABSTRACT

A bioreactor for producing synfuel from carbonaceous material includes a stacked particle heap comprising biodegradable carbonaceous material, an aerobic microbial consortium fermenting the biodegradable carbonaceous material into synfuel, and a gas impermeable barrier operatively covering the stacked particle heap. The covered particle heap is purged with at least one non-oxygenated gas. The bioreactor also includes a supply of anaerobic microorganisms which biodegrade the carbonaceous material within the stacked particle heap into synfuel. The synfuel is mixed with at least one reactor byproduct. The reactor byproducts are separated from the synfuel, which may include synthetic petroleum, alcohol, oil, and/or a gaseous fuel containing methane.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This patent application is a division of U.S. patent application Ser.No. 11/100,348, filed on Apr. 5, 2005, the entire contents of which isexpressly incorporated herein by reference.

FIELD

The present patent document relates to methods and bioreactors forbiodegrading carbonaceous material into synfuel, including, for example,synthetic oil, alcohol, and/or gaseous fuel.

BACKGROUND

The value of methane as a potential fuel source has long been recognizedand exploited. Because the current price of natural gas is about thesame as petroleum in terms of BTUs, however, natural gas has evolvedfrom a low-cost fuel source that was often a by-product of petroleum oilfield production to a fuel source worth drilling for. The increasingvalue of natural gas has been driven by a number of factors, includingthe world's shrinking supply of petroleum reserves and the increasinglystricter environmental regulations placed on coal fired power plants.Generating electricity from coal, for example, releases twice the carbondioxide as making it from natural gas. Burning coal also producesmercury vapor that has been estimated to contribute to over twentypercent of the world's mercury pollution. In addition, the burning ofcoal can release arsenic compounds and sulfur dioxide. As a result,expensive pollution control systems are now required for all new coalfired plants and most existing plants.

The demand for gases that contain methane, such as natural gas andsynthetic natural gas, will likely continue to increase in the future,not only because of the increasing demand for cleaner burning fuels, butalso because the world's demand for petroleum will continue to drive itsprice higher, particularly as known petroleum reserves are depleted. Thedemand for methane will also likely increase as hydrogen fuel cells arecommercialized. This is because the least expensive process forproducing hydrogen involves chemically converting methane and water tohydrogen and carbon dioxide in the presence of a catalyst.

To satisfy demand for natural gas, the U.S. currently imports about 2billion cubic feet of liquid natural gas (“LNG”) per day. Importing LNGhas at least two significant draw backs. First, the cost of importingLNG is high. Second, it is risky to have large LNG terminals located inmajor seaports in the present world environment, as such terminals couldbe the subject of terrorist attack. Even in the absence of terrorism,however, such terminals pose a significant explosion risk.

Because of the world's increasing demand for methane gas and cleanerburning fuels in general, alternative sources of gaseous fuels thatcontain methane are needed. As a result, an economical technique forproducing gaseous fuels that contain methane and/or a liquid synfuel,such as synthetic petroleum, would have significant market value.

Artificial gas for use as heating fuel and derived from coal or coke waswidely used during the latter part of the nineteenth century and duringthe first few decades of the twentieth century in the U.S. Because ofthe great availability and, at one time, apparent inexhaustible supplyof natural gas in the U.S., as well as a few other areas in the world,manufactured gases were phased out rapidly. The use of natural gas, onthe other hand, increased 730% between 1940 and 1970 in the U.S. Duringthis period, the U.S. gas industry produced 313 trillion cubic feet ofnatural gas. However, in other parts of the world where natural gas wasin short supply locally, manufactured gas has persisted.

Historically, the gasification of coal has involved the heating of coalthrough pyrolisis, carbonization, or retorting to cause itsdecomposition and gasification. The gas resulting from the gasificationprocess typically contains varying concentrations of carbon monoxide,carbon dioxide, methane, and hydrogen, the concentration of eachconstituent depending on the particular gasification technique employed.Thus, while gasification is the key step in these heat basedgasification techniques, it must be appreciated that it is only one stepof the overall process of forming a manufactured or synthetic naturalgas (“SNG”) from coal. In addition to the gasification step, suchprocesses typically include gas conditioning, gas purification,methanation and by-product treatment processes. Further, purification ofthe product gas from the coal gasification step to a degree of purityrequired for methane synthesis is difficult due to the large quantitiesand variety of impurities in the gas.

Another draw back of coal gasification using known heat gasificationtechniques is that the gasification process is a highly endothermicprocess, and the heat requirements of the process have to be covered bythe addition of heat. This may be accomplished through, for example,direct heat supplied through the partial combustion of the coal withoxygen or indirect heat supplied from an external fuel source. In eitherevent, however, a significant portion of the overall energy valuescontained in the coal prior to gasification are expended to gasify thecoal. Finally, the heat based gasification processes do not appear tohave any applicability to animal or plant waste, both significantrenewable resources of carbonaceous materials.

The biological conversion of organic matter into methane has also beenstudied for many years. The degradation of organic matter to methane andcarbon dioxide (i.e., methanogenic degradation) occurs in limited oxygenor other electron acceptor environments. This process is widespread inswamps, rice paddies, peat bogs, and in the intestinal tract of ruminantanimals and plays a major role in the global carbon cycle. Indeed, thetotal biological methanogenic production of methane is estimated at 500million tonnes per year, making methane the second most abundantgreenhouse gas.

Methanogenic degradation is slower and less exergonic than aerobicdegradation. However, aerobic degradation does not produce methane. Moreimportantly, methanogenic conversion only releases about 15% of theenergy that is released by complete aerobic conversion of the sameorganic carbon compound to carbon dioxide and water. This is because theremaining 85% of the energy is stored in the resulting methane forsubsequent oxidation.

Methanogens are a group of Archaea that produce methane in anaerobic oranoxic environments. They are obligate anaerobes, and thus cannottolerate any molecular or ionic oxygen in their environment. They forman interdependent relationship with other organisms, including bacteria,protozoa, insects, and grass feeding animals, such as cows. They usesimple organic compounds (e.g., formate, acetate, methyl-amines andseveral alcohols) produced by those organisms and carbon dioxide as anenergy source to produce methane.

Although methanogens depend on fermentative organisms to produce thesimple organic substrates on which they rely for energy, fermentativemicroorganisms likewise depend on methanogens to remove hydrogen and thesimple organic compounds they produce to improve their energetics. Thisinterdependence is called syntrophic cooperation. In this cooperativerelationship, the fermentative microorganism species ferment long chainorganic carbon molecules to H₂ and C-1 and C-2 compounds for themethanogens to feed upon. This fermentation process is inhibited by theH₂ and C-1 and C-2 compounds produced. Methanogens, however, obligethese fermenting species by removing the hydrogen and C-1 and C-2compounds as they convert them to methane. As a result, thesyntrophically cooperating anaerobes cooperate in the conversion ofcomplex organic matter to methane and carbon dioxide with very littleloss of the energy values contained in the original organic matter.Recent advances in molecular biology have led to a better understandingof this complex, but widespread natural process.

A more in depth review of methanogenic degradation and a list of somemethanogenic microorganisms is provided in B. Schink, Energetics ofSyntrophic Cooperation in Methanogenic Degradation, Microbiology andMolecular Biology Reviews, 61:262-280 (June 1997), which is herebyincorporated by reference.

Long before the biology of methanogenic degradation was understood,people attempted to exploit methanogenic degradation to produce methanefor its fuel value. For example, U.S. Pat. No. 1,990,523, which issuedto Buswell et al. in 1935, describes a method for methane generationusing anaerobic bacteria conversion of sewage.

Much effort has also been devoted to developing in situ microbialprocesses for the conversion of low-grade fossil fuels to methane. Forexample, U.S. Pat. No. 3,826,308, which issued to Compere-Whitney in1974, and U.S. Pat. No. 5,424,195, which issued to Volkwein in 1995,focused on treating very low-grade coal that was left behind inunderground mines. In U.S. Pat. No. 6,543,535, which issued to Converseet al. in 2003, a process for the in situ bioconversion of hydrocarbonsto methane in hydrocarbon-bearing formations is described. The processdescribed in the Converse et al. patent includes altering theenvironment of the hydrocarbon bearing formations so as to stimulate thegrowth of native microbes found within the formations.

Some of the subterranean microbial hydrocarbon conversion processesdescribed in the literature have also used explosives in an effort toincrease the surface area of coal or oil shale deposits beingmicrobially treated. The explosions create what is called a “rubblechimney.” While formation of a rubble chimney increases the rate ofconversion to methane, the overall conversion rate remains relativelyslow.

Biological processes have also been used to aid in the recovery ofpetroleum from oil reserves. For example, U.S. Pat. No. 2,413,278, whichissued to Zobell in 1946, U.S. Pat. No. 2,807,570, which issued toUpdegraff in 1957, and U.S. Pat. 2,907,389, which issued to Hitzman in1959, teach ways to use bacteria to generate extra recovery of petroleumfrom oil reservoirs after 40 to 50% of the contained oil has beenremoved by pumping and water flooding. The process of using bacteria torecover additional oil from underground reservoirs is called MicrobialEnhanced Oil Recovery (MEOR).

One of the major limitations of in situ microbial gasification and MEORprocesses is not the general ability of the bacteria used in thoseprocesses to dislodge oil, reduce viscosity or convert oil to methane,but rather the problems encountered with providing the right environmentfor microbial growth in the deep underground reservoirs or formations.Within such environments a variety of environmental factors may beencountered that individually or collectively inhibit to varyingdegrees, or even prevent, the microbial conversion or degradationprocess. Such environmental challenges can include, for example, hightemperatures, high concentrations of salts or other biocides, andlimited porosity of the native rock in which the oil is being held, asthis will restrict the accessibility of microbes to the oil. And thoughit may be possible to modify the environment of a formation to somedegree, sometimes it will not be possible or practical to alter theenvironment of a formation sufficiently to have a practical impact onmicrobial activity.

A need exists, therefore, for an ex situ process that is capable ofconverting vast quantities of low-grade fossil fuels, as well as otherorganic carbonaceous materials, into one or more synfuels, includingmethane and/or oil. While biodegradation of low-grade fossil fuels cantheoretically be performed in stirred tank bioreactors, due to therelatively long residence time that will be necessary to convert suchcarbonaceous materials to oil and/or a gaseous fuel and the large amountof material that will need to be processed to yield relatively smallquantities of fuel values, the cost of scaling a stirred tank processesup to commercial scale is simply too high to make stirred tankbioreactors a practical option. On the other hand, a very large,low-cost, yet relatively efficient, heap bioreactor could economicallyunlock the trillions of barrels of oil in the world's resources of oilshale and oil sands. Such a bioreactor could also be used in thebiogasification of other organic carbonaceous materials, includingrenewable resources such as plant and animal wastes, as well as othernon-renewable resources such as coal. The synfuel (e.g., methane,alcohol, and/or synthetic petroleum oil) produced in such bioreactorscould help fuel an energy-hungry world for the rest of the century.

In view of the foregoing, one object of the present invention is toprovide a new bioreactor design for use in converting organiccarbonaceous materials into synfuel. Another, and separate, object is toprovide a new method for converting organic carbonaceous materials intosynfuel.

SUMMARY

The present patent document is directed to methods and bioreactors forbioconverting organic carbonaceous material into synfuel. The resultingsynfuel may be, for example, synthetic petroleum, alcohol, and/or agaseous fuel containing methane.

According to one embodiment, a stacked particle bioreactor is formedfrom particles comprising biodegradable carbonaceous material. Thestacked particle bioreactor is then biotreated to convert carbonaceousmaterial within the bioreactor into synfuel, which is then collectedfrom the bioreactor. The synfuel is preferably synthetic petroleum,alcohol, and/or a gaseous fuel.

The size and size distribution of the particles used to form thebioreactor are preferably chosen so that a large percent of thecarbonaceous material is exposed to the microbes used to perform thebiotreatment. The void volume of the reactor is preferably greater thanor equal to about 15%, and more preferably greater than or equal toabout 20%. A preferred range for the void volume of the reactor isbetween about 15% and 35%, and more preferably between about 20% and35%. Preferably the void volume is substantially uniform throughout thereactor.

The biodegradable carbonaceous material treated in the bioreactor mayinclude, for example, oil sands, carbonaceous rock, asphalt, asphalticoil, waste oil, bitumen, tar, pitch, kerogen, rubber, and agriculturalwaste.

One or more cultures may be used to biotreat the stacked particlebioreactor, with each culture comprising a single type of microorganismor a group of different microorganisms. Typically, the cultures willcomprise a group of different microorganisms. Further, themicroorganisms used to biotreat the carbonaceous material in the reactormay be aerobic, facultative anaerobic, or anaerobic microorganisms. In aparticularly preferred embodiment, the biotreatment begins as an aerobicmicrobial degradation process and then is converted to an anaerobicmicrobial degradation process. In other implementations, however, it maybe desirable to perform only an aerobic biotreatment or only ananaerobic biotreatment.

If the carbonaceous material within the bioreactor is to beanaerobically biotreated, the bioreactor should be designed so that newcultures of microbes can be introduced anaerobically into the bioreactorand dispersed efficiently throughout the bioreactor.

Each of the microorganisms used to perform the biodegradation willtypically perform one of the following biochemical processes during thebiotreatment: 1) produce surface-tension reducing compounds or solventsthat release native petroleum from the carbonaceous material, 2) fermentthe carbonaceous material into smaller organic compounds, including, forexample, synthetic petroleum, alcohol and/or simple organic compounds,or 3) convert simple organic compounds resulting from the fermentationprocess into a biogas comprising methane. Thus, whether syntheticpetroleum, alcohol, a gaseous fuel, or all three are collected from thestacked particle bioreactor will depend on the feedstock, the types ofmicroorganisms used to perform the biotreatment, and the extent to whichthe digestion of the carbonaceous material within the bioreactor iscarried out.

For example, while the principal end products of aerobic degradation oforganic carbon compounds are carbon dioxide and water, in reaching thefinal aerobic degradation products, aerobic and facultative anaerobicmicroorganisms perform the first and second biochemical processesidentified above. Thus, by stopping the aerobic degradation reactionsbefore completion is reached synthetic petroleum or alcohol may beproduced from a wide variety of carbonaceous materials. Further, ifdesired, all of, or some portion of, the organic compounds producedduring the aerobic fermentation phase may be further digested andconverted to methane during a subsequent anaerobic biotreatment. Assuch, the aerobic fermentation products within the bioreactor areconsidered to be part of the biodegradable carbonaceous material in thebioreactor for purposes of the present patent document.

The principal end products of anaerobic degradation of organic carboncompounds are methane and carbon dioxide. In reaching those finaldegradation products, however, fermentative anaerobes and facultativeanaerobes will perform the first and second biochemical processesidentified above, while methanogens will perform the third. Thus, it ispossible to collect synthetic petroleum products and alcohol from thebioreactor as larger molecular weight carbon compounds are anaerobicallydegraded, particularly large molecular weight hydrocarbons. If, however,anaerobic degradation is permitted to go to completion on at least someof the organic carbonaceous material in the bioreactor, a biogascomprising methane will be produced.

After formation, the stacked particle bioreactor will continue toproduce synfuel for a period of several months or years. The liquidand/or gaseous synfuel produced in the bioreactor may be collected andremoved from the bioreactor by a network of pipes incorporated into thebioreactor during its construction.

According to another embodiment, a method of producing gaseous fuel fromcarbonaceous material using a stacked particle bioreactor is provided.The method comprises the steps of a.) forming a stacked particlebioreactor from particles that include biodegradable carbonaceousmaterial; b.) forming an anaerobic microorganism supporting environmentwithin the bioreactor; c.) anaerobically bioconverting biodegradablecarbonaceous material in the stacked particle bioreactor into a gaseousfuel; and d.) collecting the gaseous fuel from the bioreactor.Preferably the gaseous fuel produced and collected in the methodcomprises methane.

In a particularly preferred implementation of the embodiment, thestacked particle bioreactor is aerobically biotreated prior to formingan anaerobic environment within the bioreactor. This is done toaerobically ferment carbonaceous material in the bioreactor and/orrelease native oil from the carbonaceous material. Preferably, themethod also includes the step of collecting oil from the stackedparticle bioreactor.

The anaerobic environment within the bioreactor may be formed, forexample, by covering the stacked particle bioreactor with a gasimpermeable barrier, such as a clay or plastic barrier layer. Althoughthe reactor will naturally turn anaerobic with such a barrier over timeunless air or oxygen are introduced into the covered bioreactor, thebioreactor may also be purged with argon, nitrogen, carbon dioxide,ammonia or hydrogen gas to speed up the conversion of its environment toan anaerobic microorganism supporting environment. In addition topurging oxygen from the reactor, these gases may provide necessarynutrients for the microorganisms in the bioreactor or precursors formethane production (e.g., carbon dioxide and hydrogen).

If the biodegradable carbonaceous material includes particles less thanabout 0.3 cm, it may be desirable to agglomerate the particles prior toforming the stacked particle bioreactor. Preferably, the resultingagglomerates have a particle size in the range of about 0.3 cm to about2.54 cm. Alternatively, the particles of biodegradable carbonaceousmaterial may be coated on the surface of a plurality of substrateshaving a particle size greater than or equal to about 0.3 cm andpreferably less than or equal to about 5 cm, and more preferably lessthan or equal to about 2.54 cm. The coating technique is particularlyadvantageous when the substrates are significantly larger than theparticles of biodegradable carbonaceous material to be coated thereon.For the particles of carbonaceous material to properly coat on thesubstrates, typically they should have a particle size of about 250 μmor less.

According to yet another embodiment, the particles are screened into twoor more size fractions and then a plurality of stacked particlebioreactors having a void volume greater than or equal to about 15% areformed, with each bioreactor being formed from the particles from one ofthe separated size fractions. Preferably if one of the size fractionsincludes a significant fines fraction, or substantial number ofparticles less than about 0.3 cm in diameter, that size fraction ispreferably agglomerated to form particulates having a particle size inthe range of 0.3 cm to 2.54 cm before forming a bioreactor with thatsize fraction.

According to yet another embodiment, a method of convertingbiodegradable carbonaceous material into synfuel using a stackedparticle bioreactor is provided. According to the method, a stackedparticle bioreactor is formed from particles comprising biodegradablecarbonaceous material. The bioreactor is inoculated with a culturecomprising one or more aerobic and/or facultative anaerobicmicroorganisms capable of fermenting carbonaceous matter. Thecarbonaceous matter in the stack is aerobically fermented, and syntheticpetroleum and/or gaseous fuel is collected from the stack. Theenvironment within the stack is converted from an aerobic environment toan anaerobic environment, and the stack is inoculated with a culturecomprising one or more anaerobic microorganisms. The aerobicallybiotreated stack is then anaerobically biotreated to produce syntheticpetroleum and/or gaseous fuel. Finally, synthetic petroleum and/orgaseous fuel is collected from the anaerobically biotreated stack.

According to yet another embodiment, a method of bioconverting organiccarbonaceous material into synfuel using a stacked particle bioreactoris provided. The method according to the present embodiment comprisesthe steps of: a.) coating the surface of a plurality of substrateshaving a particle size greater than or equal to about 0.3 cm withorganic carbonaceous material and thereby forming a plurality of coatedsubstrates; b.) forming a stacked particle bioreactor with the coatedsubstrates, the stacked particle bioreactor having a void volume greaterthan or equal to about 15%; c.) forming an anaerobic environment withinthe stacked particle bioreactor; d.) anaerobically biotreating thestacked particle bioreactor until a desired amount of organiccarbonaceous material within the stacked particle bioreactor has beenconverted to a gaseous fuel; and e.) collecting the gaseous fuel fromthe stacked particle bioreactor.

Preferably the gaseous fuel produced and collected in the methodcomprises methane. Further, in a preferred implementation of theembodiment, synthetic petroleum is also collected from the stackedparticle bioreactor.

The plurality of substrates may comprise, for example, one or morematerials selected from the group consisting of oil shale, coal, rock,asphalt, rubber, and plant waste. Moreover, the types of plant wastethat may be used as substrates in the method include, for example, plantwaste selected from the group consisting of bark, corn cobs, nut shells,wood by-products, and crop by-products.

The organic carbonaceous material coated on the substrates may comprise,for example, an organic carbonaceous material selected from the groupconsisting of oil sands, oil shale, asphaltic oil, waste oil, bitumen,tar, pitch, kerogen, coal and agricultural waste. Further, the types ofagricultural waste that may be coated on the substrates include, forexample, manure, fruit waste, straw, fermentation waste, and pulverizedplant waste. Grape skins are a particularly preferred form of fruitwaste that may be coated on coarse substrates for biotreatment. Inaddition, rice straw is a particularly preferred form of straw that maybe coated on the substrates for biotreatment.

Notably, the energy content of one pound of rice straw is about 6,500Btu, which is similar to the energy content of some of the lignitecoals. In the Sacramento Valley alone, approximately 1,500,000 tonnes ofrice straw are produced annually. Thus, the energy content stored in theannual crop of rice straw from the Sacramento Valley is about 1.95×10¹²BTU, making it a potentially valuable renewable resource for producingsynfuel.

As used herein, the term “coal” includes all types of coals, including,in order of decreasing metamorphic rank, anthracite coal, semianthracitecoal, semibituminous coal, bituminous coal, subbituminous coal, lignitecoal, peat coal, peat, and cannel coal. If coal is used as the organiccarbonaceous material coated on the substrate, preferably the coal has ametamorphic rank of bituminous coal or less, and more preferably ametamorphic rank of peat or less. Moreover, if the organic carbonaceousmaterial coated on the substrate comprises coal or oil shale, preferablythe coating is a concentrate of these materials.

In a particularly preferred implementation of the present embodiment,the method further comprises the step of covering the stacked particlebioreactor with a gas impermeable barrier. The gas impermeable barriermay, for example, comprise a clay barrier layer or a plastic barrierlayer.

The stacked particle bioreactor is also preferably inoculated with aculture comprising one or more aerobic and/or facultative anaerobicmicroorganisms. The organic carbonaceous material in the bioreactor isthen aerobically fermented prior to an anaerobic environment beingformed within the bioreactor. Preferably, the bioreactor is aeratedduring at least a portion of the aerobic fermentation.

An anaerobic environment may be formed within the bioreactor by reducingthe oxygen concentration within the bioreactor through aerobicfermentation. Alternatively, or in addition, the stacked particlebioreactor may be purged with argon, nitrogen, carbon dioxide, ammoniaor hydrogen gas.

According to a further embodiment, a method of bioconverting organiccarbonaceous material into synfuel is provided comprising the steps of:a.) agglomerating particles comprising organic carbonaceous materialwith an agglomeration aid into a plurality of agglomerates having aparticle size greater than or equal to about 0.3 cm; b.) forming astacked particle bioreactor with the agglomerates, the stacked particlebioreactor having a void volume greater than or equal to about 15%; c.)forming an anaerobic environment within the stacked particle bioreactor;d.) anaerobically biotreating the stacked particle bioreactor until adesired amount of organic carbonaceous material within the stackedparticle bioreactor has been converted to a gaseous fuel; and e.)collecting the gaseous fuel from the stacked particle bioreactor.Preferably the gaseous fuel comprises methane as in the otherembodiments. In addition, synthetic petroleum is preferably collectedfrom the stacked particle bioreactor as it drains from the bioreactor.

The particles used to form the agglomerates may comprise a wide varietyof organic carbonaceous materials, including one or more selected fromthe group consisting of oil sands, carbonaceous rock, asphalt, rubber,and agricultural waste. Suitable agricultural wastes include, forexample, bark, corn cobs, nut shells, wood by-products, and cropby-products. Suitable carbonaceous rocks include any of the coals andoil shale. Coal particles used to form the agglomerates preferably havea metamorphic rank of bituminous coal or less, and more preferably ametamorphic rank of peat or less.

The method also preferably includes the step of covering the stackedparticle bioreactor with a gas impermeable barrier. The gas impermeablebarrier may, for example, comprise a clay barrier layer or a plasticbarrier.

The stacked particle bioreactor is also preferably inoculated with aculture comprising one or more aerobic and/or facultative anaerobicmicroorganisms. The organic carbonaceous material in the bioreactor isthen aerobically fermented prior to an anaerobic environment beingformed within the bioreactor. Preferably, the bioreactor is aeratedduring at least a portion of the aerobic fermentation.

An anaerobic environment may be formed within the bioreactor by reducingthe oxygen concentration within the bioreactor through aerobicfermentation. Alternatively, or in addition, the stacked particlebioreactor may be purged with argon, nitrogen, carbon dioxide, ammoniaor hydrogen gas.

The plurality of agglomerates may also be coated with a liquid orsemi-liquid carbonaceous material such as asphaltic oil, waste oil,bitumen, tar, pitch, and kerogen to increase the concentration ofcarbonaceous material within the bioreactor and to provide a readilybiodegradable source of organic compounds for the microorganisms tobiodegrade within the bioreactor.

According to a further embodiment, a method of converting organiccarbonaceous material into synfuel is provided comprising the steps of:a.) providing particles of solid carbonaceous organic material having aparticle size of less than about 5.0 cm; b.) screening the particlesinto two or more size fractions; c.) forming a plurality of stackedparticle bioreactors having a void volume greater than or equal to about15%, each bioreactor being formed with particles from one of theseparated size fractions; d.) forming an anaerobic environment withineach of the stacked particle bioreactors; e.) anaerobically biotreatingeach of the stacked particle bioreactors until a desired amount oforganic carbonaceous material within the stacked particle bioreactor hasbeen converted to a gaseous fuel; and f.) collecting gaseous fuel fromeach of the stacked particle bioreactors. Preferably the gaseous fuelcomprises methane as in the other embodiments. In addition, syntheticpetroleum is preferably collected from the stacked particle bioreactor.

The particles of solid organic carbonaceous material may comprise a widerange of solid organic carbonaceous materials, including, for example,oil sands, carbonaceous rock, asphalt, rubber, and agricultural waste.Suitable agricultural waste for use in the method, includes, forexample, one or more plant wastes selected from the group consisting ofbark, corn cobs, nut shells, wood by-products, and crop by-products.Suitable carbonaceous rocks for use in the method include any of thecoals and oil shale.

Preferably the method further includes the step of covering each of thestacked particle bioreactors with a gas impermeable barrier. The stackedparticle bioreactor is also preferably inoculated with a culturecomprising one or more aerobic and/or facultative anaerobicmicroorganisms. The organic carbonaceous material in the bioreactor isthen aerobically fermented prior to an anaerobic environment beingformed within the bioreactor. Preferably, the bioreactor is aeratedduring at least a portion of the aerobic fermentation.

An anaerobic environment may be formed within the bioreactor in themanner described in connection with any of the embodiments above.

Preferably a liquid or semi-liquid carbonaceous material such asasphaltic oil, waste oil, bitumen, tar, pitch, and kerogen is added toat least one of the bioreactors to increase the concentration ofcarbonaceous material within the bioreactor and to provide a readilybiodegradable source of organic compounds for the microorganisms tobiodegrade within the bioreactor.

According to another aspect of the invention, a bioreactor forconverting biodegradable carbonaceous material into synfuel is provided.According to one embodiment, the bioreactor comprises a.) a plurality ofparticles stacked to form a heap having a void volume of greater than orequal to about 15%, the particles comprising biodegradable carbonaceousmaterial; b.) means for communicating gases to the heap; c.) means forcommunicating aqueous solutions to the heap; d.) means for communicatinggas from the heap; e.) means for collecting liquids that drain from theheap; f.) a gas impermeable barrier covering the heap; and g.) amicrobial consortium within the heap capable of biodegradingbiodegradable carbonaceous material within the heap to synfuel.

Further aspects, objects, desirable features, and advantages of theinvention will be better understood from the detailed description anddrawings that follow in which various embodiments of the disclosedinvention are illustrated by way of example. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration only and are not intended as a definition of the limits ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a biodegradation power plant and itscorresponding bioreactor and associated equipment for recovering synfuelfrom carbonaceous material.

FIG. 2 is a cross sectional view of an agglomerated particle of one ormore types of organic carbonaceous materials held together with abinding agent.

FIG. 3 is a cross sectional view of a coated particle that may be usedto form a support and a coating of a carbonaceous material.

FIG. 4 is a schematic illustration of a process for producingagglomerated and/or coated particles.

FIG. 5 is a schematic illustration of a process for forming a pluralityof bioreactors according to the present invention.

DETAILED DESCRIPTION

Consistent with its ordinary meaning, the term “synfuel” is used hereinto refer to a liquid or gaseous fuel derived from a fossil fuel that issolid, such as coal, or part of a solid, such as tar sands or oil shale,or from fermentation. The synfuel produced may be, for example,synthetic petroleum, alcohol, and/or a gaseous fuel containing methane.

As used herein, the terms “biodegradable carbonaceous material” and“organic carbonaceous material” are essentially interchangeable andrefer to carbonaceous feedstock which can be used in the processes orbioreactors of the present invention to produce synfuel. It should beappreciated that those terms are also intended to encompass and refer toorganic fermentation products derived from the original carbonaceousfeedstock that are within the bioreactor.

FIG. 1 schematically illustrates a biodegradation power plant 10. Powerplant 10 includes a stacked particle bioreactor 20. In the presentembodiment, bioreactor 20 includes a heap 30 comprised of a plurality ofstacked particles and a gas impermeable barrier 36 covering heap 30.Barrier 36 is provided so that bioreactor 20 may be operated in ananaerobic mode. If bioreactor 36 will not be operated in an anaerobicmode then barrier 36 is unnecessary.

Stacked particle bioreactor 20 may be formed by stacking particlescomprising biodegradable carbonaceous material so as to form a heap 30.The stacked particle bioreactor 20 is then aerobically and/oranaerobically biotreated to convert carbonaceous material within thebioreactor 20 into synfuel, which is then collected from the bioreactor,for example, by way of liquid collection system 32 and/or gas collectionsystem 33.

The biodegradable carbonaceous material treated in the bioreactor 20 mayinclude, for example, oil sands, carbonaceous rock, asphalt, asphalticoil, waste oil, bitumen, tar, pitch, kerogen, rubber, and agriculturalwaste. Carbonaceous rock materials that may be processed in the methodsand bioreactors of the present invention include, for example, all ofthe different coals and oil shale. Lower rank coals are particularlypreferred due to the fact that they have less fixed carbon, have higherhydrogen concentrations, and are generally easier to biodegrade. Thus,it is preferred that the coal have a metamorphic rank of bituminous coalor below, more preferably of lignite coal or below, and even morepreferably of peat or below.

Both natural and synthetic asphalt may be processed in the methods andbioreactors of the present invention, thus providing a new use andalternative means of disposing of asphalt stripped from road surfaces.Similarly, shredded or ground tires may be used as a source of rubber inthe methods and bioreactors of the present invention. Agricultural wasteincludes both animal and plant waste, useful examples of which includemanure, bark, corn cobs, nut shells, wood by-products, crop by-products,fruit waste, straw, fermentation waste, and pulverized plant waste.

A large variety of stacked particle bioreactors designs may be employedto practice the methods of the present invention. In fact, many of theheap bioreactor designs used in heap bioleaching of metal ores may beadapted for use in the present invention. Further, the size and sizedistribution of the particles used to form the bioreactor 20 arepreferably chosen so that a large percent of the carbonaceous materialis exposed to the microbes used to perform the biotreatment. The sizeand size distribution of the particles are also preferably selected sothat the void volume of the reactor 20 is greater than or equal to about15% and more preferably greater than or equal to about 20%. A preferredrange for the void volume for the reactor 20 is between about 15% and35%, and more preferably between about 20% and 35%. It is also desirablefor the void volume to be substantially uniform throughout the reactor.

For bioreactors 20 that are aerobically biotreated, generally voidvolumes on the higher side of the above ranges will be desired, as goodpermeability will be needed for oxygen and liquid transfer within theheap. Although, the same level of permeability is not required forbioreactors that are to be exclusively or primarily anaerobicallybiotreated, permeability in such bioreactors remains important. This isbecause permeability is still required in such reactors for pH andtemperature control, precise low level oxygen control, and efficientchangeover to aerobic conditions within the heap. Permeability is alsoneeded to permit adequate liquid transfer within the heap so thatinoculum and nutrients can reach all areas of the reactor. Further, onetonne of coal is capable of producing as much as 0.5 tonnes of methanegas. That is about a one thousand fold volume expansion. Thus, it isimportant that the reactor have adequate permeability so as to permitthis gaseous synfuel to vent.

One or more cultures may be used to biotreat the stacked particlebioreactor 20, with each culture comprising a single type ofmicroorganism or a group of different microorganisms. Typically, thecultures will comprise a group of different microorganisms. Further, themicroorganisms used to biotreat the carbonaceous material in the reactor20 may be aerobic, facultative anaerobic, or anaerobic microorganisms,and this may change over time. For example, in a particularly preferredembodiment, the biotreatment begins as an aerobic microbial degradationprocess and then is converted to an anaerobic microbial degradationprocess. In other implementations, however, it may be desirable toperform only an aerobic biotreatment or only an anaerobic biotreatment.

If an aerobic biotreatment is to be performed, then the heap 30 ispreferably inoculated while heap 30 is being formed, or soon thereafter,with a microbial consortium that is capable of biodegrading thebiodegradable carbonaceous material that will be processed in bioreactor20. For example, inoculant may be sprayed onto the particles as they arebeing stacked, preferably conveyor stacked, to form the heap 30.Alternatively, each layer of particles laid down to form the heap 30 maybe sprayed with inoculant prior to laying down another layer ofparticles. Further, if the agglomerates or coated particles discussedbelow are used to form the heap 30, then inoculation may also occurduring the particle formation process. The foregoing inoculationtechniques are not exclusive, and those skilled in the art willappreciate from the instant disclosure that there are a wide variety ofother ways to inoculate bioreactor 20, including using the wildmicroorganism strains that are already present on the particles used toform the reactor.

If the carbonaceous material within the bioreactor 20 is to beanaerobically biotreated, then bioreactor 20 is preferably designed sothat new cultures of microbes can be introduced anaerobically into thebioreactor and dispersed efficiently throughout the bioreactor. Thismay, for example, be accomplished through an irrigation system 34, whichis in communication with a supply 40 of microbes and nutrients and water66 recovered from oil/water separator 37. In the present embodiment,irrigation system 34 is preferably a drip irrigation system so as topermit gas impermeable barrier 36 to be positioned as closely aspossible over heap 30. Irrigation system 34 is preferably positionedadjacent to the top portion of heap 30, so that all of heap 30 may beirrigated. However, it may also be desirable to have emitters 61 buriedat various depths throughout the heap, with different portions of theirrigation system being independently controllable to enhance processcontrol within the bioreactor 20.

The bacteria listed in Table 1 below may be used to aerobicallybiodegrade hydrocarbon materials found in fossil fuels such as coal, oilshale, and oil sand. In addition, wild strains found associated withthese natural resources may also be used. The typical microorganismsfound in a compost pile may be used to aerobically biodegrade theagricultural and organic waste in the bioreactor 20. Inoculum derivedfrom aerobic or facultative lagoons may also be used.

TABLE 1 Aerobic and Facultative Anaerobic Organisms Capable of DegradingLong-chain Hydrocarbons Achromobacter paraffinoclastus Acinetobactercalcoaceticus Arthrobacter paraffineus Arthrobacter simplex Candidalipolyticum Caphalosporium rosem Corynebacterium glutamicumCorynebacterium hydrocarboclastus Corynebacterium petrophilumFlavobacterium species Micrococcus glutmicus Mycobacterium parafficumMicrococcus paraffinolyticus Mycobacterium smegmatis Nocardiapetrooleophila P. aeruginosa Pseudomonas fluorescens Torulopsiscolliculosa Streptomyces argenteolus Streptomyces aureus

The facultative microorganisms in Table 1 and the microorganisms listedin Table 3 below may be used to anaerobically ferment variouscarbonaceous materials within bioreactor 20. Further, the methanogenicmicroorganisms listed in Table 2 may be used to finish thebiodegradation of the carbonaceous materials included in bioreactor 20by converting the simple organic compounds resulting from aerobic and/oranaerobic fermentation into methane. Anaerobic microorganisms useful inthe biodegradation of agricultural and other organic waste may also bereadily obtained from, for example, cow manure or the sludge offacultative or anaerobic waste treatment ponds.

The bacteria and Archaea listed in Tables 1, 2, and 3 are all availablefrom the American Type Culture Collection or like culture collections.

TABLE 2 Methanogenic Organisms Methanobacterium formicicumMethanobacterium thermautotrophicum Methanobacterium wolfeiMethanobacterium alcaliphilum Methanobacterium thermoformiciumMethanobacterium thermalcaliphilum Methanobacillus omelianskiiClostridium butyricum Pelobacter acetylenicus Methanospirillum hungateiMethanobrevibacter ruminantium Methanobrevibacter smithiiMethanobrevibacter arboriphilicus Methanothermus fervidus Methanothermussociabilis Methanosphaera stadtmanae Methanosarcina barkeriMethanosarcina mazei Methanosarcina thermophila Methanogenium cariaciMethanogenium marisnigri Methanogenium thermophilicum Methanogeniumolentangyi Methanogenium tationis Methanococcus vannielii Methanococcusvoltae Methanococcus maripaludis Methanococcus thermolithotrophicusMethanomicrobium mobile Methanomicrobium payrnteri Methanococcoidesmethylutens Methanoplanus limicola Methanolobus tindarius Methanolobussiciliae Methanolobus vulcani Methanothrix soehngenii Methanothrixconcilii Methanothrix thermoacetophila

TABLE 3 Anaerobic fermenting Microorganisms Organic Substrate DigestingAnaerobe Alcohol oxidation Desulfovibrio vulgaris, Thermoanaerobiumbrockii, Pelobacter venetianus, and Pelobacter carbinolicus. Oxidationof propionate Syntrophobacter wolinii, Syntrophobacter pfennigiiOxidation of butyrate Syntrophomonas wolfei, Syntrophomonas sapovorans,Syntrophospora bryantii Oxidation of acetate Clostridium ultunenseOxidation of glycolate Syntrophobotulus glycolicus Oxidation of aromaticcompounds Syntrophus buswellii, Syntrophus gentianae

Whether one or more of the microorganisms listed in Tables 1-3 or wildstrains are selected for use in the present process will depend onfactors such as the type of carbonaceous material being biodegraded, theexpected pH of the environment, and the expected temperatures in theheap during biodegradation. These selection criteria, however, are wellwithin the skill of those in the art and need not be described in detailhere. In general terms, however, it will be preferable to use aconsortium of microorganisms during both aerobic and anaerobicbiotreatments. Consortia of microorganisms are preferred because theenvironmental conditions (e.g., pH, temperature, Eh, nutrient types andconcentrations, organic substrates, toxin levels, etc.) will typicallyvary throughout the heap 30. Thus, when a consortium is employed, theconditions within heap 30 will naturally select for those microorganismsthat are best suited for the conditions that exist within heap 30, orsome portion of it.

Moreover, the methods and bioreactors disclosed herein are not limitedto using bacteria and Archaea to perform the biodegradation. Forexample, yeast, fungi and/or molds that biodegrades a carbonaceousmaterial within bioreactor 20 may also be used.

As noted above, the stacked particle bioreactor 20 preferably starts asan aerobic bioreactor and is then converted to an anaerobic bioreactor.The anaerobic environment within bioreactor 20 may be formed, forexample, by covering heap 30 with a gas impermeable barrier 36. Gasimpermeable barrier 36 is preferably a clay barrier layer or a plasticliner.

Once the heap 30 is covered, unless additional air or oxygen is suppliedto bioreactor 20, bioreactor 20 will naturally become anaerobic overtime because all of the available oxygen will be consumed by the aerobicbiodegradation of the carbonaceous material within bioreactor 20. As theavailable oxygen is consumed, the process within bioreactor 20 willconvert from an aerobic biodegradation process to an anaerobicbiodegradation process. To speed the conversion process up, oxygen canbe purged from the bioreactor by sweeping or purging the bioreactor witha non-oxygenated gas such as argon, nitrogen, carbon dioxide, ammonia,hydrogen or combinations thereof, as well as any other anaerobicenvironment supporting gas. The biodegradation process will also benefitfrom the use of facultative anaerobic bacteria during conversion from anaerobic to an anaerobic environment within heap 30. This is because thefacultative anaerobes can continue the degradation process while thereis still too much oxygen in the environment to support the growth ofobligate anaerobes, but insufficient oxygen for robust aerobicfermentation to continue.

Gas delivery system 60 may be used to deliver gas throughout thebioreactor. Gas delivery system 60 includes perforated pipes 31 that areburied within heap 30, preferably adjacent to the bottom portion of heap30, at the time the heap is constructed. Gas delivery system 60 alsoincludes pipe 62 which is in communication with perforated pipes 31 andselectively communicates, through valve 27, with air blower 28 orpurging gas supply 64. Prior to converting the bioreactor 20 to ananaerobic system, valve 27 is preferably positioned to opencommunication between air blower 28 and pipe 62. As a result, air fromair blower 27 can be delivered to the bioreactor 20 through perforatedpipes 31 while aerobic biodegradation is being carried out withinbioreactor 20. Thus, gas delivery system 60 may be used to adjust andcontrol oxygen levels within the heap 30 as well as to control thetemperature within the heap 30 during the aerobic phase.

Preferably, gas delivery system 60 is adapted so that it may also beused to deliver a purging gas to the bioreactor 20 in order to create ananaerobic environment within the bioreactor. In this regard, whenbioreactor 20 is to be converted to an anaerobic reactor, valve 27 ispreferably adjusted to close communication between pipe 62 and blower 28(or atmosphere). In addition, however, preferably valve 27 may also beadjusted to open communication between pipe 62 and a source of purginggas 64. Once bioreactor 20 is sufficiently purged, valve 27 may beadjusted to a third position in which communication between pipe 62 andboth blower 28 and purging gas supply 64 are shut off.

Gas collection system 33 may be used to collect and remove gaseoussynfuel from the bioreactor 20. Gas collection system 33 includes aplurality of perforated pipes 68 positioned toward the upper portion ofheap 30 during construction of heap 30. In addition, collection system33 includes a means for communicating the collected gaseous fuel, suchas pipe 70, to a holding tank 26. As the gaseous synfuel will typicallycontain a methane and carbon dioxide mixture resulting from methanogenicdegradation, preferably the captured gaseous synfuel is processedthrough a separator 39 prior to storing the desired methane fuel valuesin holding tank 26. Separator 39 is designed to separate out carbondioxide from the methane in the captured gaseous synfuel. Examples ofsuitable carbon dioxide/methane separation technologies are described inU.S. Pat. No. 4,518,399, which is hereby incorporated by reference. Theseparated carbon dioxide gas is preferably communicated via pipe 72 toconduit 62 of gas delivery system 60 and is thereby recycled to thebioreactor 20. Purified methane obtained from separator 39 may then bestored in holding tank 26 for subsequent sale or use.

Carbon dioxide from separator 39 is preferably recycled to thebioreactor 20 to maintain positive pressure within the bioreactor duringthe anaerobic phase, thereby helping to maintain anaerobic conditions byminimizing the chance for oxygen contamination. Furthermore, carbondioxide is actually one of the substrates that methanogenic organismsuse in the production of methane.

If the gaseous synfuel collected from bioreactor 20 has sufficientmethane fuel values, it may alternatively be fed directly to gas-firedelectric power generator 45. The gas-fired electric power generator maybe driven by a gas turbine or internal combustion engine adapted to runoff the collected gaseous synfuel. The power generated from thegenerator 45 may be used to provide electricity for other plantoperations, sold to a local power company, or sold directly toconsumers.

Due to the efficiency of engines and turbines, only a small percentage(24 to 38% for internal combustion engines and 16 to 18% for smallturbines) of the methane fuel values burned will be transformed intoelectrical energy. The remainder of the fuel values in the burnedmethane gas will be converted to excess heat. However, if biodegradationpower plant 10 is located near a coal, oil shale, or oil sand reserve,the excess heat produced by gas-fired electric power generator 45 may beused for a variety of purposes, including, for example, the productionof steam and/or hot water for use in extracting petroleum-like productsfrom oil sands, gasification of coal, and pyrolysis of oil shale; thuspermitting the excess heat generated from power plant 10 to be used inconventional technologies for recovering oil from these fossil fuelresources.

While all portions of heap 30 are being aerobically biodegraded, onlycarbon dioxide gas will be produced. Accordingly, a valve 71, which maybe provided in pipe 70, may be opened to vent the carbon dioxideproduced within the bioreactor.

A variety of sensors 35 may be placed at one or more locationsthroughout heap 30 to measure oxygen levels within the bioreactor 20during the biodegradation process. Sensors 35 may also monitor otherprocess parameters, including temperature, ionic strength, sulfateconcentration, toxic metal levels, pH, or Eh. Oxygen levels and othergases can also be measured by monitoring the gases traveling through gascollection system 33. Similarly, parameters such as temperature, ionicstrength, sulfate concentration, toxic metal levels, dissolved oxygen,Eh or pH can be measured within the bioreactor by monitoring liquidsremoved from the bioreactor 20 via liquid collection system 32.

Liquid collection system 32 includes a drainage system 74 built into thelowest layer of heap 30. Drainage system 74 is adapted to remove liquidsfrom the bioreactor 20 and includes a drain 80 from which fluids thatdrain from the heap 30 may be collected and recycled to the heap 30 orprocessed for their fuel values. In the present embodiment, drainagesystem 74 essentially comprises a series of French drains in that itcomprises a series of generally parallel perforated pipes 76 orientedwith their perforations toward the ground and buried in a layer ofgravel 78. Liquids that drain through perforated pipes 76 collect indrain 80 where they are preferably communicated to an oil/waterseparator 37. Liquid synfuel produced in bioreactor 20 is removed fromthe top of separator 37 and water 66 from the bottom. The liquid synfuelis communicated to tank 25 for storage pending future use or sale. Therecovered liquid synfuel may include a variety of hydrocarbons as wellas alcohols, thus, it may be desirable to further refine the liquidsynfuel prior to use or selling it on the market.

Water 66 recovered from separator 37 is preferably recycled to thebioreactor 20 through irrigation system 34, and to the extent necessarysupplemented with additional inoculant and nutrients from supply 40.Inoculant within supply 40 may come from liquid taken from differentoperating heap as a means for introducing active and adaptedmicroorganisms into heap 30. In addition to inoculant and nutrients,liquids introduced into the heap may have other agents added from supply40 as the liquid is moved back into the heap. Additional additives mayinclude, for example, water, buffering agents, sugars, waste oil,slurried cow manure. Preferably, contaminants and/or biotoxins areremoved from water 66 recovered from separator 37 before the recoveredwater 66 is recycled to heap 30.

The stacked particle bioreactor 20 will continue to produce gaseousand/or liquid synfuel for a period of several months or years. Theeventual yield of energy from the fossil fuels or other carbonaceousmaterial included in the bioreactor, however, will be high because verylittle energy will be lost to the formation of carbon dioxide as an endproduct.

After bioreactor 20 is depleted of carbonaceous material, the bioreactormay be left intact. Alternatively, it may be desirable to aerate thebioreactor to completely remove all residual hydrocarbons or othercarbonaceous material in the bioreactor. Finally, if the bioreactor isformed from coated substrates, which are discussed more fully below, thesubstrates may be recovered, recoated with more carbonaceous material,and stacked into a new heap.

Several preferred types of particles for forming heap 30 of bioreactor20 are now described in connection with FIGS. 2-5.

In general terms, heap 30 is preferably made up of a plurality of coarseparticles comprising a carbonaceous material. The particles preferablyfall within a fairly narrow size range to ensure adequate fluid flow,particularly liquid flow throughout the heap. The use of substantiallyuniform size particles to form a particular heap 30 will allow theuniform flow of liquid or gas through the bioreactor. Wider sizedistributions, on the other hand, will cause packing and reduction ofvoid volume. The void volume in the heap should generally be greaterthan or equal to about 15%, and more preferably greater than or equal toabout 20%. Typically, the void volume will be in the range of 15 to 35%.More preferably, the void volume will be in the range of 20 to 30%.Uneven packing or size segregation may cause uneven flow of gas andliquid within heap 30 and reduce the ability to control the uniform flowof liquid or gas within the stacked particle bioreactor 20.

The particles used to form heap 30 should also have sufficient integrityto be able to withstand the anticipated compression forces that will beencountered within heap 30. Typically, this will mean that the particlesshould have the ability to withstand the force of many tonnes ofmaterial stacked on top of them. And, while the particles are preferablyof a generally uniform size to promote fluid flow within bioreactor 20,they also preferably have a rough, nonuniform surface morphology to helpincrease the total surface area of the bioreactor 20.

Three methods of achieving particles with suitable characteristics forpracticing the methods disclosed herein are described in U.S. Pat. Nos.5,766,930, 5,431,717, and 5,332,559, which are incorporated herein byreference.

Agglomeration of crushed particles is one approach to increasingparticle size and thereby improve percolation of liquid through theheap. FIG. 2 shows a cross sectional view of an agglomerated particle14, a plurality of which may be used to form heap 30. The agglomeratedparticle 14 is comprised of a plurality of smaller particles 15, 16 and17 held together by a binder 18. The smaller particle 15, 16 and 17 maycomprise fines generated from crushing a biodegradable carbonaceousmaterial. Alternatively, smaller particles 15, 16, and 17 may compriseparticles from two or more different sources of carbonaceous materialthat have been combined together to make the agglomerated particle 14.Thus, it may be desirable to combine particles from two or morecarbonaceous materials having different biodegradation characteristicsto improve the overall biodegradation process within bioreactor 20. Itmay also be desirable to coat the plurality of agglomerated particles 14with additional carbonaceous material. For example, the agglomeratedparticles 14 used to form heap 30 may be coated with a slurry createdfrom biomass from ethanol fermentations, municipal waste sludge, oragricultural waste to provide nutrients to the biodegradingmicroorganisms present in the heap.

Agglomeration should be considered when the biodegradable carbonaceousmaterial to be biodegraded includes a significant fraction of particlesless than about 0.3 cm in diameter. Following agglomeration, preferablythe agglomerated particles 14 have a particle size in the range of about0.3 cm to about 2.54 cm. In this regard, if the carbonaceous material isparticularly fine grained such that it is less than about 250 μm insize, then the coating process discussed below may be a more appropriateparticle fabrication option.

A means for producing the above mentioned agglomerated particles 14 isillustrated in FIG. 4. Particles of carbonaceous material 41 that are tobe agglomerated are fed into a rotating drum 43 along with anappropriate amount of binder 18. The binder 18, for example, may belime, Portland cement or any suitable polymeric binding agent used inthe mining industry. Alternatively, it may be possible to use anotherhydrocarbon source such as asphaltic oil, waste oil, bitumen, tar,pitch, or kerogen as binder 18, but at a minimum such materials may beadded as a coating on the agglomerated particles 14.

Suitable binding agents will be those materials that bind the particlesof carbonaceous material 41 together into a plurality of relativelyuniform sized particles 14 and that produce particles that are strongenough to withstand the weight of the heap. Further, the resultingagglomerated particles 14 must be compatible with the pH of thebiological process and not prevent the access of the microbes to thecarbonaceous material to be degraded and converted to liquid and gaseoussynfuel. The methanogenic and fermentative microorganisms used in thepreferred embodiments of the present invention can grow in the pH rangeof 6 to 8 and are thus compatible with Portland cement and other neutralto alkaline pH agglomeration aids. Because microbial degradation ofcarbonaceous materials produces organic acids that can lower the pH outof the optimal range of 6 to 8, however, the use of cement as a bindermay help maintain the optimal pH range for the methanogenic anaerobes.The primary advantage of Portland cement type agglomeration aids thoughis their strength and thus non-compressibility of the particles 14 whencement is used as the binder 18.

Once the agglomerated particles 14 are formed, they can be stacked intoa heap 30 and used in the bioreactor 20 disclosed herein.

FIG. 3 illustrates a cross sectional view of a coated particle 23, asecond type of particle that may be used in the present invention. Inthis embodiment, particles of carbonaceous material 41 are coated onto aplurality of substrates 21 to form a plurality of coated particles 23having a coating 22 of carbonaceous material. Alternatively, the coating22 may include or be formed from a liquid carbonaceous material. Theparticles of carbonaceous material 41 and/or liquid carbonaceousmaterial may be coated onto the substrates 21 using a variety oftechniques, including the use of rotating drum 43 as shown in FIG. 4 ora high pulp density slurry sprayer.

The substrates 21 are preferably solid and preferably have particle sizegreater than or equal to about 0.3 cm and less than or equal to about 5cm. More preferably substrates 21 have a particle size greater than orequal to about 0.3 cm and less than or equal to about 3 cm. While thecoarse substrates 21 preferably have a particle size greater than about0.3 cm, it is recognized and contemplated that some of the substratesmay actually be smaller than this particle size. As those skilled in theart will recognize, if the coarse substrates 21 are produced by crushinglarger material to the desired size range, the crushed material willhave a certain size distribution. And even if the material is screenedto exclude material less than about 0.3 cm, some material having aparticle size less than the 0.3 cm target minimum will still be presentin the coarse substrates due to inherent inefficiencies in the screeningprocess and due to particle attrition during handling. Thus by greaterthan or equal to about 0.3 cm it is intended that substantially all ofthe coarse substrates are above this size so that the void volume of thereactor remains above at least about 20% during formation of heap 30and, preferably throughout its operation. Preferably the amount ofcoarse substrates below the 0.3 cm cutoff is less than 5% by weight.

It is desirable to form a relatively uniform coating 22 of the particlesof carbonaceous material 41 on the substrates 21 to maximize theintegrity of the coating and the surface area of the particles 41exposed to the microorganisms in the bioreactor 20. Further, as theparticle size of particles 41 decreases, the biodegradation process willproceed more quickly. Smaller particles will also tend to stick betterto substrates 21. In view of this, the particle size of the particles ofcarbonaceous material 41 is preferably less than about 250 μm, and morepreferably the nominal particle size of the particles of carbonaceousmaterial 41 to be coated on substrates 21 is greater than about 75 μmand less than about 106 μm. The thickness of the coating material ispreferably less than 1 mm to ensure that the microorganism(s) being usedto perform the biodegradation have adequate access to all of thecarbonaceous material being treated.

The total surface area of the bioreactor 20 can also be increased bydecreasing the particle size of substrates 21, using substrates 21 thathave a rough, nonuniform surface morphology and/or increasing the numberof coated substrates 23 stacked on the heap 30. The advantage ofincreasing the total surface area of the substrates within the heap isthat the amount of carbonaceous material that can be loaded onsubstrates 21 in coating 22 increases proportionately, which in turnincreases the amount of carbonaceous material that can be degraded intoliquid and gaseous fuel.

The coated particles 23 may be produced using a variety of techniques.One possibility is to add substrates 21 and particles 41 to a rotatingdrum 43 in appropriate quantities. Preferably the substrates 21 are dryand particles 41 are in a high pulp density slurry so that it will stickto substrates 21 to form coating 22. Alternatively, both substrates 21and particles 41 may be added to rotating drum 43 dry and then waterand/or other binding agent may be sprayed into the rotating drum 43 topromote adhesion of the particles 41 to the substrates 21.

An alternative method of forming coated particles 23 comprises sprayingparticles of carbonaceous material 41 in a high density slurry ontosubstrates 21 before, or as, the substrates are being stacked to formheap 30 of bioreactor 20.

A neutral to alkaline pH resistant binder 18, such as Portland cementmay be used to help hold the coated particles of carbonaceous material41 onto the solid substrate 21. However, the particles of carbonaceousmaterial 41 coated on substrates 21 may also be applied to the substratewithout a binder as well, if substrates 21 and particles 41 aresufficiently hydrophobic. An advantage of this latter approach is thatthe cost of a binding material may be avoided. A liquid or semi-liquidhydrocarbon may also be used to hold particles 41 to substrate 21 toform a coating 22 with sufficient structural integrity. Thus, forexample, asphaltic oil, waste oil, bitumen, tar, pitch, and/or kerogenmay be used to bind particles 41 to substrates 21. Or the coatedparticles 23 may be further coated with such substances to furtherincrease the content of carbonaceous matter within bioreactor 20.

The advantage of using a plurality of coated particles 23 to form heap30 over using agglomerates 14 is that the solid substrate 21 of thecoated particles 23 provides high strength to maintain the shape of theparticle. Another advantage of this embodiment is that the coating 22may be a softer hydrocarbon or biomass that could not be agglomeratedinto a particle with sufficient strength to withstand compression, butcan withstand compression when coated onto a substrate. Thus, by coatingthe softer material onto a solid support the permeability in very largeheaps can be maintained. Another advantage is that the outer coating ofhydrocarbons will be fully accessible to microbes for conversion toliquid fuel, oil and/or methane.

The substrates 21 may be created from any number of materials that arecapable of withstanding the weight of the stacked particles. Examples ofsuitable substrates 21 that do not contain any practical concentrationof carbonaceous material include barren rock, gravel, lava rock, barrenrock containing carbonate minerals, brick, cinder block, and slag.Preferably, however, substrates 21 also comprise a biodegradablecarbonaceous material that will also eventually be converted to eitheroil or methane. In this regard, the plurality of substrates maycomprise, for example, one or more materials selected from the groupconsisting of oil shale, coal, rock, asphalt, rubber, and plant waste.Examples of suitable plant waste that may be used as substrates 21include, for example, plant waste selected from the group consisting ofbark, corn cobs, nut shells, wood by-products, and crop by-products.Coal substrates may comprise any of the true coals, includingsemianthracite coal, semibituminous coal, bituminous coal, subbituminouscoal, and lignite coal.

The particles of carbonaceous material 41 coated on the substrates 21may comprise, for example, an organic carbonaceous material selectedfrom the group consisting of oil sands, oil shale, asphaltic oil, wasteoil, bitumen, tar, pitch, kerogen, coal and agricultural waste. Further,the types of agricultural waste that may be coated on the substratesinclude, for example, manure, fruit waste, straw, fermentation waste,and pulverized plant waste. Grape skins are a particularly preferredform of fruit waste that may be coated on coarse substrates forbiotreatment. In addition, rice straw is a particularly preferred formof straw that may be coated on the substrates for biotreatment. If coalis used as the organic carbonaceous material coated on the substrate,preferably the coal has a metamorphic rank of bituminous coal or less,and more preferably a metamorphic rank of peat or less. Moreover, if theorganic carbonaceous material coated on the substrate comprises coal oroil shale, preferably the coating is a concentrate of those materials.

In a particularly preferred embodiment, the particles of carbonaceousmaterial 41 forming coating 22 comprise a carbonaceous material that isreadily biodegraded, such as biomass or agricultural waste, and therebyaccelerates the overall process by providing large amounts of fattyacids to be converted into methane by the methanogenic microorganismswithin bioreactor 20.

A third method of producing particles of uniform size is illustrated inFIG. 5. In this embodiment, finer particles are removed to enhance airand liquid flow within the heap 30. Crushing and screening can removethe fine material from the crushed carbonaceous material. By removingfines before stacking, the size distribution is narrowed and thus airand liquid flow through the heap improved over the flow characteristicsof the entire crushed material. In addition to removing the fines, thecrushed rock can be further separated by size fractions. The varioussize fractions can then be stacked into separate heaps 30 or layerswithin a heap as discussed more fully below in connection with FIG. 5.

In a preferred embodiment, a carbonaceous material, such as ahydrocarbon mineral ore 51, is crushed in an ore crusher 84 to a size ofabout 5 cm or less. The crushed ore is passed through a set of screens86, 88 and 90 which separates the crushed material into two or more sizeranges. The size fractions might, for example, be separated as follows:a largest size fraction being 3 to 5 cm, a mid size fraction being 1 to3 cm, a small size fraction being of 0.5 to 1 cm, and a fines fractionbeing 0.5 cm and less. The first three separated fractions of crushedmaterial may be stacked into separate heaps according to fraction size.Thus, in the present embodiment, three heaps are formed: heap 54 for thelarge size fraction, heap 55 for the mid size fraction, and heap 56 forthe small size fraction. The carbonaceous material in the fines fraction(e.g., the carbonaceous material less than 0.5 cm in size) might be toosmall to stack into a heap without first agglomerating the fines.Accordingly, as shown in FIG. 5, the particles of carbonaceous material41 in the fines fraction may be agglomerated in an agglomeration drum92. The agglomerated particles 14 from agglomeration drum 92 may then bestacked to form heap 58 of agglomerated particles.

The formation of agglomerated particles 14 in agglomeration drum 92 maybe accomplished in the manner described above in connection with FIGS. 2and 4. The fines fraction may also be further ground and then floated toform a higher-grade carbonaceous material. The resulting flotationconcentrate may then be agglomerated in agglomeration drum 92 to formagglomerated particles 14 or coated back on the surface of the solidcrushed and sized material to form coated particles 23.

Another way of treating the fines fraction is to treat that fractionseparately from the heap bioreactor processes altogether. For example,the fines fraction may be treated in a conventional high temperatureprocess, such as in a retort.

Although the fines fraction of the present embodiment is set at 0.5 cmand below, in other embodiments it may be set differently. For example,in some implementations, it may be desirable or sufficient to set thefines fraction at particles having a particle of about 0.3 cm or less.

The size fractions of carbonaceous material collected from variousscreens, such as the large size screen 86, may be able to hold a coating22 as shown in FIG. 3. The carbonaceous material coated on the sizefraction may be coated on the plurality of substrates 21 making up thesize fraction in coating drum 53. The resulting coated particles 23 maythen be stacked, for example, in heap 54. The various types ofcarbonaceous materials that may be coated on the particles in thevarious size fractions are fully described above in connection with FIG.3. However, it is worth noting that the coating material may be a softercarbonaceous material than the hydrocarbon mineral ore being used as thesubstrate. For example, the carbonaceous material used as the coatingmaterial may be, for example, biomass, a hydrocarbon slurry, biomassfrom ethanol fermentations, municipal waste sludge, or agriculturalwaste.

Each heap 54, 55, 56, and 58 (or each layer if a stratified layerapproach is taken) will have better flow characteristics separately thanit would have if mixed together. If mixed together the smaller sizematerial will fill in the void spaces, thereby reducing void space andrestricting flow. In addition to reducing the void space some areas willinevitably have less fines and thus more void space and better flow thanothers. This disparity in flow rates will lead to channeling andnon-uniform flow around the area with excessive fines and restrictedflow. This is problematic when trying to purge oxygen out of the systemor introduce a new culture of anaerobic microorganisms.

The smallest size fraction material will have the fastest rate ofdegradation. Yet, if this fraction is stacked separately in heap 56, itwill still have uniform gas and liquid flow characteristics. The largersized material will have better flow characteristics but slower rates ofconversion to methane. The larger size fraction heap could also be usedas a support rock for a coating of softer and more readily biodegradedmaterial as described above. Also, large size fractions would havelarger void spaces and could withstand more compression and, therefore,be capable of being stacked higher than the smaller sized material. Theability to withstand more compression would make it possible to stackthe finer material as a layer on top of the larger size material. Ifstacked separately, each heap will generate oil or methane at differentrates. Once a heap is no longer producing methane at an economical rate,a new heap may be formed on top of it. At that point, it would notmatter if the remaining material in the original heap is compressed tothe point that permeability is lost. As a result, this may be the leastexpensive way to produce high strength particles for large heaps.Further, the larger size particles would not need to be re-crushed tothe smaller size ranges, which would also generate more fines andincrease cost. And, although the larger size range material willbiodegrade more slowly, because it will be able to be stacked in higherand larger heaps, heaps formed from larger size fractions of materialmay actually be able to produce the same amount of methane per squarefoot of land occupied as heaps formed from smaller size fractions.

Crushing hydrocarbon mineral ore 51, such as coal or oil shale, to atarget maximum size in the range of approximately 0.5 to 3 cm may bereadily accomplished using techniques widely known in the art. Theultimate maximum target size of the crushing operation, however, willdepend on the rate of biodegradation and the time that the heap isexpected to produce a liquid or gaseous fuel. As the size of theparticles are made smaller the surface area available to the microbialdegradation becomes larger. However, smaller crushing size targetsincrease crushing cost and the amount of fines that are too small to beincluded into the heap without agglomeration or coating as describedabove.

As will now be appreciated, the biodegradation process according to thepresent invention, and illustrated in FIG. 1, is useful for forming alarge ex situ bioreactor while insuring adequate microorganism access tothe carbonaceous material to be bio-converted into useful liquid andgaseous fuel or synfuel. Further, the enhanced liquid and gas flowprovided by the preferred embodiments allows for the easy removal ofliquid hydrocarbon fuels, such as synthetic petroleum, or gaseoushydrocarbon fuels, such as methane. The enhanced flow also allows formicroorganisms and nutrients to be introduced into the bioreactor at anytime after the formation of the heap. As illustrated in FIG. 1 anddescribed above, means may be provided at the bottom, top, andthroughout the heap 30 to facilitate the introduction and removal ofliquids and gases.

The present invention also provides a cost effective way to achieve avery large, high surface area reactor for aerobic and/or anaerobicdegradation of carbonaceous materials to synfuel. Indeed, it is possibleto cost effectively scale the methods and bioreactors of the presentinvention to process thousands of tonnes of oil shale or oil sand perday. A typical commercial development of this invention may involve, forexample, stacking 10,000 tonnes or more per day of carbonaceous materialinto heaps of up to a million or more tonnes of carbonaceous materialtotal. The ability to cost effectively scale the methods and reactors ofthe present invention to a very large scale is important, not onlybecause the conversion process will be slow, but also because it will benecessary to extract the fuel values from significant quantities ofcarbonaceous material to make a material impact on the world's petroleumsupply. To put this in perspective, it would, for example, be necessaryto extract the fuel value from approximately 100,000 to 400,000 tonnesof oil shale per day to replace about 1% of the US's current 10 millionbarrels of oil imported each day.

In light of the foregoing advantages, the methods and bioreactor designsdescribed in the instant patent document are particularly well suitedfor deriving synfuel from low-grade fossil fuels. This is because it ispossible with the methods and reactors of the present invention toprocess large quantities of such fossil fuels in a very large, low-costprocess, which is crucial considering the long residence times that willbe necessary to biodegrade those fossil fuels into synfuel and theconcentration of energy values in those fossil fuels per tonne ofmaterial. Because oil shale, oil sands, peat and low-grade coal tend tobe closer to the surface, however, they will tend to be relativelyinexpensive to mine, thus keeping the costs of building the bioreactorrelatively low in comparison to the recoverable fuel values added to thebioreactor. On the other hand, deeper deposits of carbonaceous rock willcost more to mine, thus potentially impacting the economics of theprocess negatively even though the mined carbonaceous rock may be ofhigher grade.

In considering the potential value of the present invention, and itseconomics, it is worth reviewing some noteworthy facts regarding some ofthe low-grade fossil fuels that may be processed in the presentinvention.

Oil shale—The total world resources of oil shale are estimated at over2.6 trillion barrels of oil, with one of the largest deposits beinglocated in the U.S. Thus, reserves of oil locked in oil shale dwarfknown petroleum reserves by several time over. Oil shale typicallycontains 10 gal or more of oil per tonne of shale, with large quantitiesof shale in the U.S. containing over 20 gal/tonne or even 30 gal/tonne.Indeed, it is estimated that in the Green River formation in the U.S.there are 731 billion barrels of oil in shale reserves that contain atleast 25 gal of oil per tonne of shale. If such shale can be processedfor a price of $5 per tonne or less, the process will clearly beeconomical. Considering, however, that the cost of processing a tonne ofore in heap bioleaching techniques in the mining industry is in therange of $2 to $5 per tonne, processing shale at a cost of $5 or lessper tonne is very feasible.

Oil sands—Oil sands of the world contain the largest accumulations ofliquid hydrocarbons in the earth's crust. Sometimes called tar sands andbituminous sands, oil sands contain a heavy viscous petroleum substancecalled asphaltic oil. The largest reserves of oil sands in the world arelocated in Alberta, Canada, which have been estimated to contain overone trillion barrels of oil. Another deposit of oil sands in SouthAmerica is said to contain 692 billion barrels of oil. Oil sandstypically contain from 0.5 to 1 barrel of oil per tonne.

Low rank coal—The U.S. has significant reserves of low rank coal, suchas brown coal and peat, as well as other humic substances. Moreover, theU.S. has the world's largest peat reserves. Peat has a persistently highmoisture (minimum 75%), which typically requires it to be dried beforeit is burned in other processes. Peat may be used in the presentprocess, however, without drying it first, thus saving a substantialamount of money in processing this resource.

High sulfur petroleum and coals—Due to environmental restrictions onsulfur dioxide emissions these fossil fuels can only be burned in plantshaving adequate pollution control systems or the sulfur must be removedprior to burning the fuels. In the present invention, however, highsulfur fossil fuels may be readily processed.

A preferred embodiment for producing and recovering a liquid hydrocarbonfuel from tar sands or oil sands and oil shale is provided. Tar or oilsands and oil shale contain a large amount of hydrocarbons. Someportions of the hydrocarbons can be washed off or removed with water andelevated temperatures. In addition, products of aerobic microbialfermentation of these hydrocarbons will aid in the removal of thehydrocarbon. For example, microbes of the genus Arthrobacter, BacillusCorynebacterium, Pseudominass and others listed in Table 1 above producesurfactants and solvents that will aid in dislodging oil held on thesurface of the sand and shale of these hydrocarbon sources.

In addition to these microbially produced extraction agents, microbesare capable of reducing the molecular weight of paraffinic hydrocarbonsand thereby lowering their viscosity. The resulting lower viscosity oilmay then be removed more readily from the sand and shale by water flow.

Thus, the biological process of mobilizing oil is a way of enhancing theextraction of oil contained within the oil sand or oil shale. Inaddition to producing extraction agents useful in the separation ofhydrocarbon values from minerals, the microorganisms convert thehydrocarbons to lower molecular weight petroleum oil. Further, theaerobic microorganisms used to produce extraction agents and reduce theviscosity of the oil will produce, through further biodegradation, smallorganic molecules which may be subsequently consumed by methanogenicmicroorganisms and converted to methane and carbon dioxide. Whilemicroorganisms available from culture collections may be used, wild typemicroorganisms isolated from the hydrocarbon site itself are likely tobe the most useful to include in the heap culture.

The released oil may subsequently be extracted from the minerals in theheap using the broth from the aerobic fermentation. As described above,the oil mobilization bacteria can be added to the heap of agglomeratedoil sand or oil shale as the heap is being formed or shortly thereafter.This aerobic part of the process starts the mobilization and viscosityreduction of the heavy hydrocarbons and tars into removable oil that iseluded out of the heap by the flow of liquid through the heap particlesand into the liquid collection system 32 where it is then provided tooil/water separator 37, and the separated oil collected in tank 25.

After the heap is covered or sealed the process can be converted to ananaerobic environment by sweeping bioreactor 20 with carbon dioxide orby letting the aerobic microbes consume the entrapped oxygen. Theprocess of oil removal may still continue because anaerobic microbes canstill mobilize oil by producing surfactants and solvents.

As the heap becomes anaerobic, methanogenic microorganisms areintroduced into the heap 30 through irrigation system 34 to startgenerating methane. These strictly anaerobic microorganisms can beobtained through culture collections, some of which are listed in Table2. In addition to obtaining methanogens from culture collections, mixedculture can be isolated under anaerobic conditions from peat bogs,sewage treatment plants, rice paddies, and the intestinal tracks ofruminants. In this part of the process the residual hydrocarbons andorganic compounds produced by the aerobic part of the process areconverted to methane. In addition, during this part of the process theoxygen level and other parameters such as temperature, pH, solutionchemistry, sulfate levels, and toxic metals should be monitored usingsensors 35 or other means discussed above. Adjustments can be made tothe heap environmental conditions by controlling the gas and liquid flowto the heap via gas delivery system 60 and irrigation system 34.

The anaerobic phase of this process will take longer than the aerobicphase of the process. Further, the surface hydrocarbons on the particlesthat make up the bioreactor will be converted to oil and methanefastest. Later in the process, the microbes will consume the moreembedded hydrocarbons within the particles. The total time and rate ofmethane generation will be a function of the size, distribution of theparticles and the biodegradability of the carbonaceous material. Mostcoal, for example, will biodegrade anaerobically to methane, but at avery slow rate. A solid support made of low-grade coal may take severalyears to be converted to methane. A layer of tar sand coated onto thesolid coal support may be converted to liquid oil and methane within thefirst year of the process. A layer of biomass or agriculture wastecoated onto coal support may be converted to methane in a few months.The rapid growth of microbes on the outer layer of more susceptibleorganic material will facilitate the biodegradation of the moreresistant solid support by accelerating the rapid development of a thickcoating of actively growing microbes over all the solid supportparticles.

After the outer layers are degraded and most of the easily accessiblehydrocarbons are converted to oil or methane the need for void space andgood flow characteristics within the heap are diminished. Therefore, newheap bioreactors may be constructed on top of the older heap bioreactorsthat have consumed most of the outer softer material. At that point, theolder heap in the slower part of the methane generation cycle may bebetter able to accommodate the extra weight of another heap or liftbuilt on top of it.

The following prophetic examples further define the invention and shouldnot be construed as limiting the invention to the examples set forth.For example, the specific examples described below are directed atbiodegrading oil shale, oil sand, coal, and peat. However, as describedabove, the device and method according to the present invention may beused to biodegrade all types of biodegradable carbonaceous materials.

EXAMPLE 1

In this example, a solid hydrocarbon containing material such as oilshale is used in a heap bioreactor 20 to produce both oil and methane.The oil shale is mined and crushed to a size of less than 5 cm with anaverage size fraction of about 3 cm. As illustrated in FIG. 5, thesmaller size fraction of less than about 1 cm is agglomerated intolarger particles of about 3 cm. A polymeric or Portland cement binder 18may be used to help form stable agglomerates. It is recognized thatanother hydrocarbon source such as tar or high viscosity oil may act asa suitable agglomeration aid or may be coated on the surface of theagglomerate. Another way of treating the fines is to remove them fromthe heap process altogether. Further grinding and flotation may be usedto form a higher-grade hydrocarbon that can then be agglomerated orcoated back on to the solid crushed and sized material. Alternatively,the fines fraction may be processed in a conventional high temperatureprocess, such as in a retort.

The size of the particles is chosen by a compromise between cost and therate of oil and gas production. The smaller size range of 1 to 3 cm willgive faster oil and methane production. The large size range 3 to 5 cmwill cost less to crush and produce less of the fines that will need tobe removed or agglomerated. A mixture or larger size range of 1 cm to 5cm will pack more tightly and restrict gas and liquid flow. It would bebetter to stack two separate heaps or lifts of two size ranges (1-3 cmand 3-5 cm) than to combine them. Therefore, it is beneficial to testeach of the sizes or size ranges to determine the relative rates oforganic carbon and hydrocarbon degradation and extraction and methanegeneration. This may be done in a small-scale laboratory test for eachtype of hydrocarbon mineral to be processed at commercial scale. Thistype of test will determine the rate of oil and methane production withtime. Microbes used in the test and the environmental conditions such astemperature, pH and nutrients will also affect the rate.

As the agglomerates are being made, or as the heap is being stacked, aconsortium of hydrocarbon degrading microbes is added to the heap. Theconsortium should be a mixed culture of microbes of aerobic andfacultative anaerobic microorganisms that are known to degradehydrocarbons of the type being treated in the heap process. Morespecifically, the mixed culture should be adapted to feed on thehydrocarbon source being treated in the heap. Methods of isolating andadapting microorganisms for hydrocarbon degradation of petroleum oil aregenerally known by those skilled in microbiology. One method of microbeadaptation is taught by Ikeda et al. in U.S. Pat. No. 5,919,696, whichis hereby incorporated by reference.

The heap will be aerobic during the time that it is being stacked.Perforated pipes 31 and 76 in gas delivery system 60 and liquidcollection system 32, respectively, are laid down first and covered withrock or the heap particles directly. As the heap is stacked higher,irrigation system 34 and gas collection system 33 are placed in theheap. These may be at the top and midsection of the heap. Sensors 35 maybe added to the heap 30 to monitor various process parameters, includingtemperature, oxygen concentration, pressure and pH, and transmit thedetected information to controller, not illustrated herein.

In the aerobic phase of the process microbes feed on the hydrocarbons toproduce bio-surfactants, solvents, and heat that help dislodge andmobilize the petroleum contained in the oil shale. In addition, themicrobes bring about chemical changes to the viscous hydrocarbons thatreduce the viscosity of the oil contained in the shale. This oilmigrates to the lower part of the heap to be removed by the liquidcollection system 32. Water may also be used as a carrier to help sweepthe oil off of the stacked particles. The aqueous solution and oil arethen collected in an oil/water separator 37 where the oil can beseparated from the aqueous solution and then provided to tank 25 forstorage. The separated water may then be circulated back into the heapthrough irrigation system 34. Alternatively, the water can be removed aswaste.

The aerobic process may continue after the heap is stacked and coveredwith an impermeable liner 36, for example a clay cap or plastic liner.The length of time will depend on the material being processed and theeconomic value of liquid oil vs. methane. The process is changed from anaerobic process to an anaerobic process by stopping the flow of airthrough the gas delivery system 60 built into the heap or by sweepingthe heap with a low oxygen (less than 1.0%) gas mixture. A possible gasmixture could be nitrogen and carbon dioxide. The aerobic microbes willbreak the higher molecular weight hydrocarbons to smaller molecules.This will help the start of methane generation during the anaerobicprocess. However, the aerobic process will waste more of the energypotential of the hydrocarbon fuel by degrading the hydrocarbon all theway to carbon dioxide, water and heat. Economics will determine the besttime to convert the heap from the faster aerobic process to the sloweranaerobic methane generation process.

Careful control of oxygen levels may be needed to optimize methanegeneration without hydrogen sulfide generation. Sulfate reducingbacteria will compete with methanogenic microbes for the acetate, fattyacids and hydrogen produced by fermenting anaerobic microbes. Thesulfate reducing bacteria will produce hydrogen sulfide and not methane,thereby decreasing the efficiency of the process.

Strictly anaerobic methanogenic microorganisms may need to be suppliedto the heap after it has become anaerobic because they may not have beenable to survive the aerobic part of the process. These methanogenicmicroorganisms may be obtained from an existing heap operating in theanaerobic mode, as such a heap is a source of adapted and activelygrowing microorganisms. During the anaerobic phase liquid oil may stillbe produced and collected. The methane gas is produced until most of theavailable hydrocarbon has been converted to liquid petroleum/oil ormethane. The time will depend on the size of the particles or the crushsize of the shale being processed. A smaller crush size than 5 cm willcost more to produce but will produce oil and methane faster.Experimentation and economic analysis can determine the best crush sizefor a particular shale.

EXAMPLE 2

In this example the hydrocarbon source is oil sand. This material isalso called tar sands and contains bitumen similar to oil shale. AlbertaCanada has three of the world's largest oil sand deposits, which areconservatively estimated at over one trillion barrels. Bitumen makes upabout 10-12% of the oil sands. The remainder is 80-85% sand and clayminerals and 4-6% water. Only about 10% of these deposits are consideredrecoverable with conventional hot water extraction or flotationenrichment technology. These non-biological extraction processes leaveabout 25% of the bitumen in an alkaline tail.

In this example, the oil sands material is agglomerated into smallpellets or particles of about 1 to 3 cm in size. The size of theparticles biotreated should be selected based on the rate at whichmicrobes will reduce the viscosity of the heavy oil and extract it fromthe particles. This can be determined in laboratory experimentation aswas done in Example 1. In general, smaller particles will yield more oilat a faster rate than the larger particles. However, the smallerparticles may be more expensive and difficult to produce.

In addition to determining the appropriate particle size, theappropriate amount and type of binder may be experimentally determinedusing techniques known in the mining art. The selected binder should bestrong enough to hold an agglomerated particle 14 together and resistthe weight of the heap. The amount of the binder used, however, shouldnot be so much that the penetration of microbes or extraction of oil isprevented. Also the use of excess binder will increase the cost of theprocess. Suitable binders include, for example, Portland cement andpolymers. Flotation concentrate of bitumen may also be agglomerated intothe particle or coated onto the outer surface of the particle. Theamount of cement used will typically be in the range of about 1 to 3%.

The agglomerated particles 14 are inoculated with an adapted consortiumof microbes that are capable of reducing the viscosity of bitumen andconverting it to lighter molecular weight oil. This consortium should bea mixed culture of aerobic and facultative anaerobic microorganisms thatare known to produce surfactant solvents and heat that help dislodge theoil. The mixed culture should also contain thermophiles that can survivethe higher temperature that results from the heat released by theaerobic hydrocarbon degradation. The heap should be designed andoperated to conserve the heat generated because it will aid in the oilextraction.

The heap will start as an aerobic process as in Example 1. Gas deliverysystem 60, irrigation system 34, and liquid collection system 32 may bebuilt into the heap to inject process gas and water and collect drainagewater that contains extracted oil and process water. As the heap isstacked higher, irrigation system 34 and gas collection system 33 areplaced in the heap. The process water collected in liquid collectionsystem 32 is separated from the oil in oil/water separator 37 and thenreconditioned for re-injecting and reuse through irrigation system 34.The reconditioning step may include pH adjustment and removal of toxicmaterials that may retard bacterial growth. Also new microbes could beadded to this process water. Those might be strictly anaerobicfermenting and methanogenic microbes for the production of methane.

In addition to the irrigation system and liquid collection pipes, theheap is constructed with gas supply and removal pipes 31, 68. The supplypipes 31 are necessary to inject gas mixture that can control oxygenlevels within the heap. During the aerobic part of the process theoxygen level can be from 1-10% or more to stimulate bitumen degradationand conversion to liquid oil. After most of the recoverable oil isremoved, the oxygen level is reduced to facilitate methane generation.The remaining oil and low molecular weight organic compounds and theaerobic microbes themselves are quickly converted to acetate and otherone or two carbon compounds by anaerobic fermenting microbes. Anaerobicmethanogenic bacteria then convert these compounds into methane, whichis collected through the gas collection system 33.

The process then proceeds more slowly as the anaerobic consortium offermenting and methanogenic microbes continue to degrade the highermolecular weight bitumen or other organic hydrocarbon sources. Thisslower process may go on for several years. The gas generated willcontain a mixture of methane and carbon dioxide. A more highlyconcentrated methane gas can be produced by removing the carbon dioxidefrom the gas mixture means of separator 39. The purified methane gas canbe sold as natural gas. Alternatively, if not already of sufficientconcentration in pipe 70, the gas can be cleaned up enough to be burnedin electric power generator 45 to provide heat and/or electricity.

EXAMPLE 3

The U.S. and other countries throughout the world have vast amounts ofmineable coal. Unfortunately, many of these sources of coal are of lowgrade or are high in sulfur or ash and are not useful for powergeneration for environmental reasons. Stricter air quality requirementshave reduced the usefulness of many of these coal sources. Most newpower generating plants are designed to use cleaner burning natural gas.

In this example, low-grade coal is converted to cleaner burning methanegas by anaerobic bioconversion of coal to methane in a large ex situheap 30 of crushed and sized coal. The solid nature of coal and itscomplex chemical structure make it slow to be microbially converted intomethane. Thus, in addition to inoculating with fermenting microbes andmethanogenic microbes, a good source of nutrients and growth substrateshould also be combined with the coal. The substrate, nutrients andmicrobes can be mixed or agglomerated or coated onto the coal particlesas they are being stacked into the heap 30. Some good sources of growthsubstrate materials are biomass from ethanol fermentations, municipalwaste sludge, and agricultural waste. These will provide organicmaterial for microbial growth and will also help make the heap anaerobicby consuming oxygen. The more easily degraded organic substrate willstimulate the growth of a large amount of microbes that will cover allthe coal particles.

The size range of the coal particles should be determined in laboratorytests to determine the rate of coal to methane conversion as a functionof size or surface area to volume. One method of performing these testsis to set up a number of columns each containing different size rangeseach mixed with ample nutrient and microbe cultures. The columns arekept anaerobic and the amount of generated methane measured. In additionto columns, small stirred reactors can be used to measure rates ofbio-methane generation for much higher surface area to volume ratiosthen would be used in a large-scale process. The results from this labtest could then be used to estimate rates of methane generation forlarge-scale field heaps.

This type of testing will allow for optimization of pH, temperature, andother environmental conditions that will be used to model and control alarge commercial operation. Models of the system could also be useful topredict and control the rate of methane generation. Several heaps ofdifferent size ranges may be constructed to produce methane at differentrates as a method of configuring production rates to meet anticipatedmethane demand.

In this example, a large heap may be constructed nearby an old coalfired power plant that is in the process of converting to a gas-firedpower plant. Coal that is brought into the power plant that no longermeets air quality emission standards could be crushed to theexperimentally determined size then size separated for one or more heapsor lifts of different size ranges. The finest size range could beagglomerated and stacked in another heap. Each heap or lift will startto produce methane that may supply a gas-fired turbine electricitygenerator. The cleaner burning coal may continue to be used to generateelectric power from the existing coal-fired power plant. In this way thefacility could continue to produce as much power as it had before anddecrease emissions. This type of change over would also make use of muchof the existing facility.

EXAMPLE 4

Peat bogs harbor approximately 30% of the world's soil carbon reserves.The natural biodegradation of peat accounts for 3 to 7% of the globalmethane emissions. Peat is young coal and the U.S. has the secondlargest peat resource in the world. The total energy contained in theU.S. peat resources is estimated at the equivalent of about 240 billionbarrels of oil. It is evenly distributed throughout the country and isat the surface with little or no overburden.

Peat bogs are generally acidic and anoxic with methanogenic methaneproduction as the major microbiological process. However, the top layerof peat contains methanotrophic microbes that consume much of themethane produced and oxidize it to carbon dioxide and water. The totalmethane emission from peat bogs is less than 0.1 liters per square meterof surface per day.

Peat can be dewatered and burned for fuel directly. For a number ofreasons, including the cost of dewatering, this is not generally done inthe U.S., although it is in other parts of the world. In this example,the peat is removed from the bog and made into small pellets orparticles to be stacked into the bioreactor. Because of peat's highwater content and its soft and compressible nature it should undergosome processing to reduce the compressibility before it is stacked intoa heap. In addition to changing its physical properties, addition ofnutrients, pH adjustment and microbial inoculation can be when the heapbioreactor is being formed.

To strengthen the peat particle, a binding agent can be added. Portlandcement can function as a binding aid and be used to adjust the pH of thepeat. Further, methanogenesis at neutral pH can use a wide range ofsmall organic compounds to produce methane. Thus, laboratory testing ofmethanogenic methane production can be analyzed as a function of pH,nutrients, and other environmental requirements for the particular peatexample. The optimum pH, nutrients, and other conditions may then beadjusted to as the agglomerated particles 14 are produced. In otherwords, other material 15 and 17 can be agglomerated into the particles14 to help create the optimum environment and strength of theagglomerated particles 14. In addition to cement, or carbonate rock forstrength and pH control biomass or agriculture waste or sludge can beadded to provide nutrients and microbes. Alternatively, to provide lesscompressible particles, the peat may be coated onto a plurality of solidsubstrates 21, such as coal, oil shale, or rock, as illustrated in FIG.3.

The resulting peat particles are stacked into a heap 30, as previouslydescribed. The heap will start as an aerobic process but will change toan anaerobic process as the oxygen is swept out or consumed. The heap isalso covered with an impermeable gas barrier 36 to prevent theintroduction of unwanted oxygen. The height of the heap is limited bythe compressibility and permeability of the heap particles. The heapmust remain permeable enough after it is stacked that liquid canpercolate through the heap to bring in nutrients, microbes, and controlpH. In addition, it must be gas permeable enough that methane can beremoved and oxygen levels controlled.

The rate of methane generation will depend on the microbes ability toferment the complex peat organic material into acetate, and other simpleorganic materials. These simple fatty acids and hydrogen and carbondioxide can be converted into methane. It is anticipated that the rateof methane production should be increased over 10 fold more than therate of methane generated from peat bogs. Acidic peat bogs produce 6 to30 g of methane per tonne of peat per day. The heap bioreactor 20described in this example should, however, be capable of producing morethan 300 g of methane per tonne of peat per day.

Although the invention has been described with reference to preferredembodiments and specific examples, it will readily be appreciated bythose skilled in the art that many modifications and adaptations of themethods and bioreactors described herein are possible without departurefrom the spirit and scope of the invention as claimed hereinafter. Thus,it is to be clearly understood that this description is made only by wayof example and not as a limitation on the scope of the invention asclaimed below.

1. A method of bioconverting organic carbonaceous material into fuelusing a stacked particle bioreactor, the method comprising the steps of:a. coating the surface of a plurality of substrates having a particlesize greater than or equal to about 0.3 cm with organic carbonaceousmaterial and thereby forming a plurality of coated substrates; b.forming a stacked particle bioreactor with the coated substrates, thestacked particle bioreactor having a void volume greater than or equalto about 15%; c. forming an anaerobic environment within the stackedparticle bioreactor; d. anaerobically biotreating the stacked particlebioreactor until a desired amount of organic carbonaceous materialwithin the stacked particle bioreactor has been converted to a gaseousfuel; and e. collecting the gaseous fuel from the stacked particlebioreactor.
 2. A method according to claim 1, further comprising thestep of collecting synthetic petroleum from the stacked particlebioreactor as it drains from the bioreactor.
 3. A method according toclaim 1 or 2, wherein the plurality of substrates are comprised of atleast one material selected from the group consisting of oil shale,coal, rock, asphalt, rubber, and plant waste.
 4. A method according toclaim 3, wherein the plurality of substrates comprise plant wasteselected from the group consisting of bark, corn cobs, nut shells, woodby-products, and crop by-products.
 5. A method according to claim 1 or2, wherein the organic carbonaceous material coated on the substratescomprises an organic carbonaceous material selected from the groupconsisting of oil sands, oil shale, asphaltic oil, waste oil, bitumen,tar, pitch, kerogen, coal and agricultural waste.
 6. A method accordingto claim 5, wherein the organic carbonaceous material coated on thesubstrates comprises agricultural waste.
 7. A method according to claim6, wherein the agricultural waste is selected from the group consistingof manure, fruit waste, straw, fermentation waste, and pulverized plantwaste.
 8. A method according to claim 5, wherein the organiccarbonaceous material coated on the substrates comprises coal and thecoal has a metamorphic rank of bituminous coal or less.
 9. A methodaccording to claim 5, wherein the organic carbonaceous material coatedon the substrates comprises coal and the coal has a metamorphic rank ofpeat or less.
 10. A method according to claim 5, wherein the organiccarbonaceous material is a concentrate made from oil shale.
 11. A methodaccording to claim 1, further comprising the step of covering thestacked particle bioreactor with a gas impermeable barrier.
 12. A methodaccording to claim 11, wherein the gas impermeable barrier is selectedfrom the group consisting of a clay barrier layer or a plastic barrier.13. A method according to claim 1, wherein the step of forming ananaerobic environment includes purging the stacked particle bioreactorwith argon, nitrogen, carbon dioxide, ammonia or hydrogen gas.
 14. Amethod according to claim 1, further comprising inoculating the stackedparticle bioreactor with a culture comprising one or more aerobic and/orfacultative anaerobic microorganisms and aerobically fermenting organiccarbonaceous material in the bioreactor prior to forming an anaerobicenvironment within the bioreactor.
 15. A method according to claim 14,further comprising aerating the bioreactor during at least a portion ofthe aerobic fermentation.
 16. A method according to claim 14, whereinthe step of forming an anaerobic environment includes reducing theoxygen concentration within the stacked particle bioreactor throughaerobic fermentation.
 17. A method according to claim 1, wherein thegaseous fuel comprises methane.
 18. A method of bioconverting organiccarbonaceous material into fuel using a stacked particle bioreactor, themethod comprising the steps of: a. agglomerating particles comprisingorganic carbonaceous material with an agglomeration aid into a pluralityof agglomerates having a particle size greater than or equal to about0.3 cm; b. forming a stacked particle bioreactor with the agglomerates,the stacked particle bioreactor having a void volume greater than orequal to about 15%; c. forming an anaerobic environment within thestacked particle bioreactor; d. anaerobically biotreating the stackedparticle bioreactor until a desired amount of organic carbonaceousmaterial within the stacked particle bioreactor has been converted to agaseous fuel; and e. collecting the gaseous fuel from the stackedparticle bioreactor.
 19. method according to claim 18, furthercomprising the step of collecting synthetic petroleum from the stackedparticle bioreactor as it drains from the bioreactor.
 20. A methodaccording to claim 18 or 19, wherein the particles comprise an organiccarbonaceous material selected from the group consisting of oil sands,carbonaceous rock, asphalt, rubber, and agricultural waste.
 21. A methodaccording to claim 20, wherein the particles comprise agricultural wasteand the agricultural waste comprises at least one plant waste selectedfrom the group consisting of bark, corn cobs, nut shells, woodby-products, and crop by-products.
 22. A method according to claim 21,wherein the particles comprise carbonaceous rock and the carbonaceousrock comprises coal or oil shale.
 23. A method according to claim 22,wherein the carbonaceous rock comprises coal having a metamorphic rankof bituminous coal or less.
 24. A method according to claim 22, whereinthe carbonaceous rock comprises coal having a metamorphic rank of peator less.
 25. A method according to claim 18, further comprising the stepof covering the stacked particle bioreactor with a gas impermeablebarrier.
 26. A method according to claim 18, further comprisinginoculating the stacked particle bioreactor with a culture comprisingone or more aerobic and/or facultative anaerobic microorganisms andaerobically fermenting organic carbonaceous material in the bioreactorprior to forming an anaerobic environment within the bioreactor.
 27. Amethod according to claim 26, wherein the step of forming an anaerobicenvironment includes reducing the oxygen concentration within thestacked particle bioreactor through aerobic fermentation.
 28. A methodaccording to claim 18, further comprising coating the plurality ofagglomerates with at least one material selected from the groupconsisting of asphaltic oil, waste oil, bitumen, tar, pitch, andkerogen.